The invention relates to the field of stator assemblies of the type used in concert with high-speed spindle elements. More specifically, the invention relates to stator assemblies utilized in a disc drive system.
Disc drive memory systems have been used in computers for many years for storage of digital information. Information is recorded on concentric memory tracks of a magnetic disc medium, the actual information being stored in the form of magnetic transitions within the medium. The discs themselves are rotatably mounted on a spindle. The information is accessed by means of read/write heads generally located on a pivoting arm that moves radially over the surface of the disc. The read/write heads or transducers must be accurately aligned with the storage tracks on the disc to ensure proper reading and writing of information.
During operation, the discs are rotated at very high speeds within an enclosed housing by means of an electric motor generally located inside a hub that supports the discs. One type of motor in common use is known as an in-hub or in-spindle motor. Such in-spindle motors typically have a spindle mounted by means of two ball or hydrodynamic bearing systems to a motor shaft disposed in the center of the hub. Generally, such motors include a stator comprising a plurality of teeth arranged in a circle. Each of the teeth support a plurality of coils or windings that may be sequentially energized to polarize the stator. A plurality of permanent magnets are disposed in alternating polarity adjacent the stators. As the coils disposed on the stators are sequentially energized in alternating polarity, the magnetic attraction and repulsion of each stator to the adjacent magnets cause the spindle to rotate, thereby rotating the disc and passing the information storage tracks beneath the head.
As the coils on the stator are sequentially energized to generate the rotational force, the stators begin to vibrate. Additionally, tolerance stacks across the drive components result in gaps therebetween in a direction along the spindle axis. The energization of the coils produces a solenoid effect in this direction that causes the drive components to move in response to the motor switching, thereby creating an axial vibration. When the resonant frequency of these components, including the stator, is near the switching frequency of the motor, there is little damping of vibrations. Such vibrations, whether in the form of structural mechanical resonances or the forced response of a thin surface member, tend to produce acoustic noise that is irritating to many users and conveys the appearance of an inferiorly constructed unit.
Thus, the problem presented is to minimize the vibrations and noise contribution produced by the stator during motor operation.
In one aspect of the invention, a disc drive spindle motor having improved acoustic properties is provided. In one embodiment, the disc drive spindle motor includes a base, a stationary member, a rotor and a stator. A bearing interconnects the rotor with the stationary member and allows the rotor to rotate about the stationary member. The stator includes a plurality of teeth supported from a stationary support member. The teeth have a plurality of coils wound thereover. At least one stiffening member is coupled to the stator, joining the teeth at an end opposite the stationary support member. The stiffening member substantially reduces and/or tunes vibrations in the stator thereby reducing acoustic noise generated by the motor.
In another aspect of the invention, a disc drive storage system having a stiffened stator is provided. In one embodiment, the disc drive storage system generally includes a housing, a stator, a rotatable member and at least one data storage disc that is coaxially attached to the rotatable member. The housing includes a base that has a stationary member attached thereto. The stationary member is coaxial with a central axis of the base. The rotatable member is interface by a bearing with the stationary member. The stator, also coaxial with the rotatable member, includes a plurality of teeth extending from an annular support member. At least a first annular stiffening member is bonded between the ends of the teeth which minimizes and/or tunes the vibration and acoustic noise contribution of the stator during the system""s operation.
While the invention is useful in disc drive spindle motors having ball bearings, the invention is particularly useful in hydrodynamic bearing motors to reduce or eliminate pure vibration tones that become more noticeable with lower levels of background vibration. Additionally, the invention may be used to tune the frequency of the stator away from excitation frequencies of other components of the motor. The stiffened stator can have an axial position that is within or below the hub, and can have a radial position that is internal or external to the rotor. The mass of the stiffening member may be tuned to shift the frequency of the stator away from frequencies of other drive components.